Abstract

Hydrogen peroxide is a treatment used in the salmon industry for sea lice control. The action mechanism to detach lice from their host has been proposed through mechanical paralysis induced by bubbles in the hemolymph. However, the molecular responses of lice and fish treated with hydrogen peroxide have not been characterized. This study aimed to evaluate the efficacy of hydrogen peroxide (PARAMOVE (R)) and explore the transcriptome modulation of exposed lice and Atlantic salmon during the infective process. To test the efficacy, small-scale treatment with infested-Atlantic salmon were conducted using 0, 600, 800, and 1200 ppm of hydrogen peroxide for 20 min. A positive correlation between the number of detached lice and the hydrogen peroxide concentrations was observed. Females collected from hydrogen peroxide treatments evidenced a reduced larval viability compared with the control group and correlated with the concentrations. Furthermore, lice exposed to PARAMOVE (R) evidenced significant regulation of genes associated with antioxidant system and reproduction. Notably, transcriptome analyses in fish exposed to hydrogen peroxide showed high modulation of genes associated with response to drugs, response to stress and oxidative stress, hypoxia, and proteolysis. The results strongly suggest that the hydrogen peroxide impacts the reproductive process, possibly reducing the larval viability from exposed females. This study uncovers the molecular responses produced by the hydrogen peroxide treatments, providing new information for sea lice control in the salmon industry.